Diagnosing and Treating Rare Infectious Diseases Presenting as Acute Abdominal Pain

Introduction:

Acute abdominal pain can be caused due to many infectious microorganisms like bacteria, viruses, and parasites. Often, parasitic infections go undiagnosed and untreated as the clinical features mimic the other common causes of acute abdominal pain. The diseases caused by most parasites result in significant morbidity and mortality among vulnerable populations. Abdominal parasitosis may flare up and make the patient end up in a casualty if left untreated. A clinician equipped with a thorough insight into the clinical manifestations and life cycle of parasites in the host environments, diagnosis, and treatment protocols can manage infectious abdominal parasitosis effectively.

What Are the Infectious Diseases Causing Acute Abdominal Pain?

1. Hydatid Cyst:

a. Etiology:

• Hydatid disease is also called cystic echinococcosis. It causes infection in humans, mainly in the larval stage of the dog tapeworm, Echinococcus granulosus.

• Echinococcus granulosus is a pathogenic parasite that causes infection in humans by zoonosis, following the ingestion of tapeworm eggs excreted through the feces of the infected dogs.

• Hydatid disease has become a huge endemic health problem in various parts of the world.

b. Pathophysiology:

• The liver is most commonly affected. The lung, the spleen, the kidney, the bones, and the brain are also relatively infected.

• The cyst formed can rupture, causing dissemination or anaphylactic reactions in the peritoneum or biliary tract.

• Infection of the cyst can lead to the development of liver abscesses and local complications like cholestasis, portal hypertension, and Budd-Chiari syndrome.

c. Clinical Features:

• Right upper quadrant or epigastric pain.

• Cough, low-grade fever.

• Abdominal fullness.

• Bloody stools.

• Coughing.

• Hepatomegaly.

• Chills.

• Skin rash.

• Shortness of breath.

• Jaundice.

• Unexplained weight loss.

d. Diagnosis:

• The definitive diagnosis of hydatid cysts requires a combination of imaging, serologic, and immunologic studies.

• Past and recent infections are most commonly diagnosed by serological tests, which detect parasite-specific antibodies in the sample.

• Exposure to parasitic infection can be detected by the presence of IgG antibodies, and active infection is associated with elevated levels of specific IgM and IgA antibodies.

• Postoperative monitoring, efficiency of pharmacotherapy, and prognosis are assessed by the presence of circulating hydatid antigen in the serum.

• ELISA (enzyme-linked immunosorbent assay) is used most commonly in the diagnosis. However, alternate techniques like counter-immuno-electrophoresis and bacterial co-agglutination are also employed.

• CT (computed tomography) scan serves as an important diagnostic tool as it detects biliary or extrahepatic extension and also aids in the identification of complications, such as rupture and infections.

• An elevated diaphragm and a thin rim of calcification suggest the presence of a cyst. This can be viewed in plain radiographs of the abdomen and chest.

• Ultrasonography is currently the diagnostic tool of choice, with an accuracy of 90 percent.

e. Complications:

• Intrabiliary rupture (rupture of the hydatid cysts occurs, causing the inflow of the cystic contents into the biliary system.

• Septicemia (refers to poisoning of the blood when an infection from a different site enters the blood).

• Hepatomegaly (enlargement of the liver).

• Anaphylaxis (a serious life-threatening allergic reaction involving the whole body).

f. Treatment:

• Surgery is the treatment of choice for hydatid cysts. Surgical intervention inactivates the parasite, evacuates the cyst by resecting the germinal layer, prevents the peritoneal spillage of scolices, and obliterates the residual cavity.

• A laparoscopic approach to hydatid cysts is associated with better outcomes, lower morbidity, and need not require a prolonged hospital stay.

• PAIR (puncture, aspiration, injection, and re-aspiration) is a percutaneous treatment technique for the removal of hydatid cysts. It is minimally an invasive method, which is carried out by a needle guided by ultrasound into the cyst.

• Benzimidazole carbamates, such as Mebendazole and Albendazole, are the drugs given to reduce the size of the cyst.

• Albendazole is more effective as it can undergo better penetration and absorption.

2. Anisakiasis:

a. Etiology:

• The gastrointestinal tract of marine animals harbors a parasite called anisakiasis.

• The free-swimming larvae are excreted after getting hatched and are ingested by fish and squid.

• Humans acquire this rare paracytic disease by ingestion of raw, contaminated, undercooked seafood. This condition is prevalent in areas where raw fish is consumed as a traditional food.

• When humans acquire this infection, larvae burrow into the stomach and small bowel, causing tissue damage.

b. Pathophysiology:

• Once the larvae attach themselves to the gastrointestinal wall, it causes ulceration, granulomatous inflammation, or perforation.

• The inflammation caused may trigger a localized allergic reaction or an IgE-mediated systemic allergic reaction.

• The majority of the cases present gastric involvement.

c. Clinical Features:

• Abrupt abdominal pain.

• Nausea and vomiting.

• Fever.

• Diarrhea.

• Peritoneal irritation.

• Intestinal obstruction due to intussusception.

d. Diagnosis:

• Ultrasound is commonly used when a patient presents with epigastric or right upper quadrant pain. Further, the technique shows diffuse concentric wall thickening in gastric or intestinal walls, hypoechoic submucosal edema, irregularity of the lumen surface due to edema of the Kerckring’s folds (corn sign), and free fluid accumulation around the involved segment can be seen.

• A CT scan is advised in case of gastric and intestinal involvement, which shows gastric or intestinal wall thickening due to submucosal edema.

• Endoscopy also aids in accurate diagnosis.

e. Treatment:

• Endoscopic removal of the larvae is beneficial. It is a curative procedure.

• Management of intestinal anisakiasis can also be done by pharmacotherapy using antihelminthic drugs like Albendazole.

• Albendazole of 400 mg is given twice a day orally for about six to 21 days.

3. Dientamoebiasis:

a. Etiology:

• Dientamoeba fragilis (D.fragilis) is a protozoan parasite found in human feces.

• Until recent times, this unusual parasite was regarded as non-pathogenic.

• Studies now reveal its association with the infectious cause of abdominal pain and other clinical manifestations.

b. Clinical Features:

• Abdominal pain.

• Diarrhea.

• Loose or abnormal stools.

• Fecal urgency.

• Nausea and vomiting.

• Fever.

• Eosinophilia.

c. Diagnosis:

• Since time immemorial, the detection of D. fragilis through microscopic staining of fixed fecal smears has been the most common practice.

• Parasitic culture techniques have also been employed in detecting the presence of D. fragilis.

• Polymerase chain reaction (PCR) has gained popularity in the early detection of the parasite in the sample, and the result can be obtained within hours to initiate the definitive treatment process.

d. Treatment:

• Paromomycin of 8 to 12 mg/kg orally is given daily for seven to ten days, or Iodoquinol of 650 mg orally is given daily for ten to 12 days, and combination therapy of Doxycycline of 100 mg and Iodoquinol of 650 mg orally is given daily for ten days.

• Secnidazole, Nitazoxanid are also used to treat dientamoebiasis.

Conclusion:

Many parasitic infections present as acute abdominal pain. The clinical diagnosis of these parasitic diseases is often delayed as they mimic the clinical features of other diseases behind acute abdominal pain. Hence, parasitic infections should be included in the differential diagnosis of acute abdominal pain, especially in patients from known endemic areas. Appropriate imaging techniques detect parasitic involvement and can assist in the timely diagnosis, favoring better treatment outcomes.